The present invention relates generally to semiconductor processing systems, and more specifically to a system and method for transferring a wafer or other planar type substrate to a processing apparatus.
The fabrication of integrated circuits and other type devices typically employs a series of fabrication steps in which a semiconductor wafer or other type substrate is processed within various processing systems. For example, a semiconductor wafer is subjected to photoresist and other film depositions and patterning steps, implantation and diffusion type processing, etc. The diverse processing steps are executed in a variety of different processing systems, for example, photoresist ashing systems, dry etch systems, ion implantation systems, chemical vapor deposition systems, etc. For each of the above processing systems, control of contamination is imperative for a cost-effective, reliable manufacture of such devices. Furthermore, because design rules for integrated circuits require ever-decreasing critical dimension feature sizes, it is necessary to provide improved control over particulate contamination within such systems.
Some of the primary sources of particulate contamination in integrated circuit processing are personnel, equipment and chemicals. Particulates generated or xe2x80x9cgiven-offxe2x80x9d by personnel are transmitted through the processing environment and may result undesirably in device defects. Particulates within the equipment and chemicals associated therewith are often called process defects and are caused by frictional contact between surfaces in the equipment and impurities within the supply gases or chemicals. One significant source of such process defects is contamination associated with the storage transportation of wafers from one processing system to another. Various mechanisms have been developed to isolate the wafer from particles during the storage, transport and processing of wafers in the processing equipment. For example, the Standard Mechanical Interface (SMIF) system has been created to reduce particle contaminations.
In a typical SMIF system, a box or carrier is placed at the interface port of the processing apparatus; latches release the box door and port door simultaneously. The doors on the carrier mate with the doors on the interface port of the processing equipments and open simultaneously so that particles which may have been on the external door surfaces are trapped between the doors and thus do not contaminate the processing chamber.
Regardless of the various attempts made to minimize process defects, contamination problems still persist. Another method of reducing process defects associated with such contamination is by constantly evacuating and re-pressurizing the process chamber as wafers are transferred thereto and therefrom. A method for effectuating such contamination reduction is illustrated in prior art FIG. 1 and designated generally at reference numeral 10. Typically, a multi-wafer cassette is located local to the processing chamber at ambient atmosphere, while a wafer within the process chamber is processed at a substantially reduced pressure, for example, about 1 millitorr at step 12. After the processing is complete, the wafer is removed at step 14 by opening the process chamber to allow transfer of the processed wafer back into the multi-wafer cassette.
Subsequent to the wafer removal, the process chamber is pumped down to a pressure significantly lower than the processing pressure, for example, about 1 microtorr at step 106 in order remove any contamination that may have been introduced by opening the chamber door. A load lock valve is then opened and a new wafer is then loaded into the process chamber at step 18. The load lock valve is then closed and the chamber is again pressurized to the desired process pressure at step 20. Although the above method 10 generally is effective at minimizing contamination to a reasonable level, the method 10 involves xe2x80x9cpump and ventxe2x80x9d cycles between the loading of each wafer into the chamber which negatively impacts processing throughput. As is well known to those skilled in the art, because processing equipment is a significant capital expenditure, low equipment throughput is highly undesirable.
Another problem associated with certain types of semiconductor processing equipment is related to the doorway or access port into the process chamber. Typically a wafer transfer endstation mates with a rectangular or box-like doorway or access port of the process chamber. The process chamber isolates the internal portion of the chamber from the outside environment during processing by actuating a slot valve associated with the access port. The slot valve-access port interface, however, results in an asymmetry within the process chamber which in some processes, for example, plasma immersion ion implantation, may result in temperature variation, plasma density non-uniformity and other type non-uniformities within the process. Such non-uniformities may negatively impact process control and the like.
There is a need in the art for a semiconductor processing system and method which minimizes process chamber contamination, increases wafer throughput and improves semiconductor process control.
The present invention is directed to a wafer processing system which efficiently handles the transfer of wafers to and from a wafer processing chamber in a manner which reduces chamber contamination, increases wafer throughput and improves process control.
According to one aspect of the present invention, a wafer processing system and associated method is disclosed which efficiently handles the transfer of a wafer to and from a wafer processing chamber without requiring an evacuation of the processing chamber for each wafer transfer. The system includes a load lock chamber, a process chamber and a transfer chamber therebetween. A portion of the load lock chamber is sealed or otherwise isolated from the transfer chamber and the process chamber when a wafer is transferred thereto. The load lock chamber portion is then evacuated or otherwise pumped to substantially equalize the pressure between the load lock chamber portion and the remaining portion of the load lock chamber, transfer chamber and process chamber. Upon pressure equalization, the load lock chamber portion containing the wafer is brought into fluid communication with the transfer chamber and the process chamber, and the wafer is transferred to the processing chamber via the transfer chamber. According to the present invention, the use of one or more such load lock chambers allows transfer of wafers to the process chamber without the need for an evacuation thereof, thereby minimizing process chamber contamination and increasing wafer throughput.
According to another aspect of the present invention, a ring valve and associated method is disclosed. The ring valve resides within or is otherwise associated with the process chamber and is operable to move between an open and closed position therein to selectively seal the process chamber from the remainder of the wafer processing system. In the open ring valve position, the interior of the processing chamber forms a top chamber portion and a bottom chamber portion defining an annular spacing therebetween. In the open position, the ring valve exposes a process chamber access port at a portion of the annular spacing through which the transfer chamber is coupled and the process chamber is accessed. In the closed position, the ring valve couples the top and bottom interior chamber portions together, thereby sealing the processing chamber from the transfer chamber and load lock chamber, respectively. In addition, the ring valve has a substantially uniform interior peripheral surface which provides a peripheral uniformity within the processing chamber, thereby facilitating uniform processing conditions therein.
According to yet another aspect of the present invention, a single axis wafer movement transfer arm and associated method of wafer transfer is disclosed. The transfer arm avoids the multi-axis, multi-jointed articulated robotic arms of prior art systems, thereby reducing the particle generation and contamination associated therewith. The transfer arm includes an elongate member which is rotatably coupled to a portion of the transfer chamber about an axis which permits rotational movement of the transfer arm between the load lock chamber and the process chamber. Preferably, the arm is rotatably coupled to the transfer chamber at a midpoint thereof and contains end effectors at each end for simultaneous wafer transfer between the process chamber and the load lock chamber in an efficient manner.
Preferably, the transfer arm of the present invention is utilized in conjunction with a dual load lock chamber processing system arrangement. In such case, two such transfer arms are implemented and rotate about separate axes to and from the process chamber from separate load lock chambers. That is, one transfer arm rotates about a first axis while the other transfer arm rotates about a second axis. In the above manner, one load lock chamber may be loaded externally with a wafer and undergo a pump and vent cycle while the other load lock chamber is transferring and receiving thereto wafers with the process chamber. In the above manner, wafers are transferred to and from the process chamber in an efficient manner without substantial contamination associated therewith, thereby improving process yield and throughput.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.